Nucleotide

A review of nucleotide biochemistry describes nucleotides as phosphate esters of nucleosides that function in all cellular processes, beyond their role as the building blocks of DNA and RNA [1]. One familiar example is ATP, an adenine nucleotide with three phosphate groups, which also acts as a neurotransmitter [6].

Other nucleotides help build cell membranes. The pyrimidine nucleotide CTP, which cells also make from UTP, contributes to the synthesis of phosphatidylcholine and phosphatidylethanolamine in the brain through a route called the Kennedy pathway (mechanism, not a measured outcome) [2].

Nucleotides also occur in food. A 2000 review of milk constituents noted that the European Commission had allowed specific ribonucleotides to be added to infant and follow-on formula [3]. The same review also explained that digestion converts dietary nucleic acids and nucleoproteins into nucleosides and nucleobases, the forms preferred for absorption in the intestine; the Nucleoside entry covers that step [3].

Citicoline is the clearest case on NootropicsWork. A 12-week trial in healthy older adults, funded by the ingredient supplier Kyowa Hakko Bio, describes citicoline (CDP-choline) as a naturally occurring mononucleotide, meaning a single nucleotide unit [4].

A supplement's chemical class describes its structure. Whether it changes an outcome is a separate question, graded on each compound page.

• Nucleoside: a nucleotide without its phosphate [1].
• Mitochondria: the sites where oxidative phosphorylation forms ATP, a nucleotide [7][6].
• Citicoline: the compound page grades the trial evidence.